This invention relates to protector apparatus for oil-filled submergible electric motors that drive submergible pumps and is concerned, more particularly, with the provision of a wide variety of protectors economically.
Oil-filled submergible electric motors that drive submergible pumps in deep wells are commonly provided with protectors (or seal sections) to perform three functions: (1) pressure equalization between the motor oil and the well fluid, (2) accommodation of internal fluid volume change with temperature, and (3) support of pump-produced axial thrust load. The two major types of protectors are positive separation protectors and labyrinth protectors. See, e.g., U.S. Pat. Nos. 2,569,741 and 2,783,400 assigned to the assignee of the present invention. Positive separation protectors employ expansible chambers, such as bags, cylinders with pistons, bellows and the like. Labyrinth protectors employ circuitous fluid flow paths and rely upon the immiscibility and difference in specific gravity (density) of motor oil and well fluid to provide a movable interface between fluids to be separated. Sometimes a "barrier" fluid is employed to separate motor oil and well fluid in order to reduce mixing of the fluids to be separated. In some labyrinth-type protectors used with motors completely filled with an oil which is more dense than the well fluid, the labyrinth is employed to prevent particulates from entering a thrust bearing chamber and the motor.
Usually, all of the functions of the protector are performed within a single section of the equipment string (including the motor, the pump, the protector and other components). Occasionally, however, certain functions are divided between two or more parts. For instance, volume accommodation and pressure balance may be performed by a bellows or bag within the bottom portion of the motor housing, while an additional protector may only contain seals, a thrust bearing, and, in most instances, a pressure relief mechanism.
The manufacture of a wide variety of protectors to accommodate different needs and preferences has necessitated maintenance of a large inventory of different parts and finished assemblies and has required the use of substantially different manufacturing procedures. Such specialized protector manufacture is disadvantageous.